Hydraulic transmission



Oct, 7, 1941. D. w. FLETCHER HYDRAULIC TRANSMISSION Filed sept. 25, 19:59

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Oct. 7, 1941. D, W FLECHER, 2,257,792

IDRAULIC TRANsMIfssON Filed Sept. 25, 1939 3 Sheets-Sheet 3 Patented Oct. 7, 1941 UNITED STATES PATENT OFFICE .,25'1,792\l HYDRAULIC 'raANsMrssIoN` Daniel W. Fletcher, Toronto, Ontario, Canada Application September 25, 1939, Serial No. 296,392

1 Claim.

'I'his invention relates to hydraulic transmissions, and more particularly to the type in which primary and secondary pumps are used for varying the speed or reversing the direction of movement of the driven member of the transmission, and my object is to provide simple apparatus of this character which may be made cheaply and yet be durable and efficient.

I attain my object by providing a drive shaft along which are disposed the secondary or control pump, two disks and the primary or motor pump. The cylinder block of the secondary pump and one of the disks, which is provided with an eccentric for the primary pump, are k'eyed on the drive shaft. The cylinder block of the primary pump is secured to the driven shaft. The eccentric for the secondary pump is movable relative to the drive shaft to vary the stroke of said pump and is carried on a slide which is guided on the adjacent end wall of a stationary casing for housing the pumps and the disks. The slide is moved by means of an eccentric which may be manually or automatically controlled to cause the speed of the driven member to be varied.

The constructions are hereinafter more fully described and are illustrated in the accompanying drawings in whichl Fig. 1 is a longitudinal section of the transmission taken on the line I-I in Fig.

Fig. 2 a cross section on the line 2-2 in Fig. 1;

Fig. 3 a cross section on the line 3-3 inFig. l;

Fig. 4 a cross section on the line 4-4 in Fig. 1;

Fig.`5 a cross section on the` line 5-5 in Fig. 1, the outer rim of the cylinder block being omitted and the stationary disk being shown in side elevation on said line 5-5; and

Fig. 6 a` detail in perspective of a portion of the eccentric'straps.

In the drawings like numerals of reference indicate corresponding parts in the different figures.

and 2 are the drive and driven shafts respectively which are suitably journalled in bearings carried by the opposite end walls of a casing 3. The cylinder block 4 of the secondary pump 5 is provided with a hub 6 which is keyed at 1\to the drive shaft. The hub is journalled in a stationary disk 8 which contacts with a rotatable disk 9 keyed at I0 to the drive shaft. The side face of the rotatable disk 9, remote from the stationary disk 8, has an eccentric formed thereon for actuating a primary pump I2. The cylinder block I3 of the pump I2 has a hub I4, on which the eccentric is journalled,l

and a hub I5 which is suitably secured to a flange i6 on the driven shaft 2. The end of the drive shaft I adjacent the driven shaft 2 is journalled in the hubs I4 and I5 of the cylinder f block so that the said end is supported from the bearing foi` the driven shaft 2.

The cylinder block |3 of the primary pump I2 has a plurality of radially disposed bores I1 in which pistons I8 are tted. -The pistons are connected by 'rods I9 with an eccentric strap 20 on the eccentric Il. The construction of the secondary pump 5 is similar to that of the primary pump |2 except the bores 2|, in the secondary pump cylinder block 4, and the-pistons 22 therein are larger in diameter than the bores I1 and pistons I8 of the primary pump. The pistons 22 are connected by rods 23 with an eccentric strap 24 on a non-rotatable eccentric 25 which is freely disposed on the drive shaft I and adjustable relative thereto to vary the stroke 'of the secondary, pump pistons.

The eccentric 25 is provided With a vertical slot 26 through which the drive shaft I passes, and is carried on a slide 21 mounted in a guide 28 on the adjacent end wall of the casing 3. The slide is vertically adjusted by means of anl eccentric 29 which operates in a horizontal opening 30 in the slide. The eccentric 29 is secured to a spindle 3| which is journalled in the aforesaid end wall of the casing and is provided with a crank arm 32 which may be manually or automatically operated.

The cylinder block 4 is provided with ports 33 which form communications between the bores 2| and one or the other of tWo circumferentially separated grooves 34, 31|a formed at the same radius in the face of the stationary disk 8 in contact with said block 4. Each of the grooves extends slightly less than 180 around the face of the disk. The grooves are separated by the dams 34b arranged diametrically opposite one another so that all the pump cylinders or bores 2| on the pressure side of the eccentric 25 will be in communication with one of the grooves While the other pump cylinders 2| on the suction side of the eccentric will be in communication with the other of the grooves. Thus, as the cylinders 2| revolve, their ports will communicate flrst with one groove 34, 34B and then with the other, the dams 34b being adapted to prevent communication with both grooves at the one time.

The cylinder block I3`of the primary pump I2 is also provided with ports 35 forming communications between the bores |1 and one o r the other of two ciicumferentally' separated grooves 36, 36* formed in the face ofthe rotary disk 9 in contact with said block I3. These grooves are similar tothe grooves 34, 34ai and are separated by dams 36h which are diametrically opposite one another so that all the pump cylinders or bores |1 on the pressure side of the eccentric II will be in communication with one of the grooves while the other cylinders I1 on the suction side of the eccentric will be in communication with the other groove.

In the contacting faces of the stationary and rotary disks 8 and 9 are formed two annular pas- 4 sageways 31 and 38. The disk 8 is provided with passages 39 and 40 forming communications between the passageways 31, 38 and the grooves 34, 34a respectively. The grooves 36, 36a in the disk 9 communicate by passages 4| and 42 with the passageways 31, 38 respectively.

When the transmission is in neutral or is operating to drive the driven shaft 2 in the same direction of station as the drive shaft up to a one to one drive ratio between said shafts, oil or other ud in the pump cylinders I1 may pass freely from the ports 35 on the high pressure side uf the primary pump I2, as positioned in the drawings relative to the grooves 34 and 34,

through the groove 3GB, passage 42, passageway 38, passage 40, groove 34a to the ports 33 communicating with the cylinders 2| on the low pressure side of the secondary pump 5. The cylinders 2| on the high pressure side of pump 5 will then be in communication with the low pressure side of the primary pump I2 by means of the other ports 33, the groove 34, passage 39, passageway 31, passage 4I, the other groove 36 and the other ports 35 communicating with the cylinders I1 on the low pressure side of the primary pump I2. 'I'he flow of oil from one pump to the other is thus in a closed circuit which is adapted to be maintained full of liquid as hereinafter described.

Assuming the control eccentric 29 is positioned at N, as shown in full lines in Fig. 2, the drive shaft I is rotated, and the capacities of the primary and secondary pumps are equal, the oil will ow as described in the preceding paragraph but, because of the equal capacities of the pumps, the cylinder block I3 will not be rotated. As the eccentric 29 is moved towards the position indicated at H, the eccentric is moved by the slide 21 to decrease the stroke of the pistons 22 of the secondary pump 5 until the eccentric 25 is concentric with the shaft I. During this movement of the eccentric 25, the capacity of the secondary pump is gradually decreased which results in the cylinder block I3 being rotated and its speed being increased until a one to one drive ra 'Wis established which occurs when the capaci y of the secondary pump is zero.

A continued movement of the control eccentric 23 from the position H to the position indicated at O causes the center of the eccentric 25 to move past the center of the drive shaft I whereby the initially high pressure cylinders Aor bores 2| of the secondary pump' become low pressure cylinders or bores and the previously low pressure `cylinders 2| become high pressure cylinders which causes the direction of flow of fluid to be reversed. The high pressure flow is therefore from the secondary pump 5 to the high pressure When the control eccentric 29 is moved to the position indicated at R the capacity of the secondary pump 5 is greater than that of the primary pump- I2 whereby the rate of flow from the high pressure side of the secondary pump to the low pressure side of the primary pump is increased which results in the direction of rotation of the primary pump cylinder block I3 and thus of the driven shaft 2 being reversed.

The casing 3 is maintained lled with oil from a reservoir 43 into which a pipe 44 is directed for venting the casing. Any oil carried by air or gas through the pipe 44 will thus discharge into the reservoir. Any oil leaking from the circuit is replenished by the supply in the reservoir. The stationary disk 8 carries two oil lines 45, 46 which communicate with the grooves 34, 34 respectively on opposite sides of a dam 34". The oil lines 45, 46 are connected by a horizontal tube 41 which is provided with two sets of check valves 48, 49 whereby oil may be drawn into the low pressure groove 34 or 34a and the high pressure groove 34 or 34 will communicate with an air dome 50 and an oil cooler 5I. thev inlet check valves 48 may thus be used to draw in oil from-the casing to one of the grooves 34, 34, and either of the check Valves 49 may be employed to establish communication between the other of the said grooves and the tube 41. The ow of oil through the cooler will be controlled by a valve 52.

The eccentric straps 20 and 24 are identical in construction although they might diier in size. Each strap comprises inner and outer rings 53 and 54 which are adapted to be fitted on an eccentric or 25. The inner ring is provided with two spaced apart ilanges 55 which extend slightly less than 180 circumferentially of the ring and project laterally to overlie the outer rings. The latter are joined together by a band 56 which overlies slightly less than 180 of the unanged portion of the inner ring 53. The band is provided with flanges 51 which are also spaced apart and extend around the band. The inner ring anges and the outer ring anges are each rigidly connected substantially midway of their ends with diametrically opposite connecting rods having T ends 58, While the other connecting rods of each pump are pivotally mounted on pins 59 which are carried by the anges and extend across the spaces therebetween. With this arrangement the rods are maintained at their most eicient angle to re- -duce wear on the walls of the cylinders and pisside of the primary pump I2 which increases v the speed N'` the primary pump cylinder block of the drive shaftsk I3 and thus that of the driven shaft 2 in excess 7 ns. What I claim asv my invention is:

In a hydraulic transmission the combination with driving and driven members, of means including primary and secondary pumps for causing the driven member to be actuated from the driving member, a stationary ,casing for housing said` pumps, the primary pump including a cylinder block connected with the driven member and having a plurality of radially disposed bores therein; pistons in said bores; a disk rotatable with the driving member and provided with an eccentric; means operated by the eccentric for actuating the pistons, the secondary pump including a cylinder block rotatable with the drEng member and having a plurality of radially disposed bores therein; a stationary disk arranged beside the rotatable disk, the disks being between the 'cylinder blocks and having two annular passageways formed in their contact- 5 ing faces, each disk also being provided with Either. ofl

ltwo circumferentially separated grooves in face in contact with the adjacent cylinder block,

v the grooves being of thesame radius. and each groove extending slight-lyless than 180 around the face of the disk, one of the grooves in each disk being in communication with one of the annular passagewaysand the other4 of the` grooves in each disk being in communication with the other of the annular passageways; ports doggy/92 pistons of thesecondary pump; and means for moving'the eccentric relative to the driving member to vary the stroke oi' the secondary in each cylinder block forming communications lo between each bore and one or the other of the pump pistons, Y DANIEL W. FLETCHER. 

